1. Field of the Invention
The present invention relates to a plastic pallet and more particularly to a pallet made of synthetic resin for use with a fork lift. Further, in a specific aspect, the present invention relates to a plastic pallet having a fork-inserting mouth on each of its four sides with the mouths of adjacent sides being at different levels.
2. Description of the Prior Art
Heretofore, the material most commonly used for constructing a pallet for a fork lift has been lumber. However, lumber is not entirely satisfactory because of certain natural deficiencies, such as the limitation of natural resources, unstable supply, poor chemical resistance of the product, and the necessarily complicated manufacturing methods employed to make them. Metallic pallets also are available, but they are expensive. Therefore, recently, attempts have been made to produce a plastic pallet.
As is well known, however, a pallet for a fork lift is usually constructed from two sheets of deck board joined by parallel girder materials provided at their respective opposite edges and intermediate portions whereby a space is provided between the girder portions for receiving the fork. Therefore, a shortcoming of these conventional plastic pallets is that they compare unfavorably with the wooden or metallic pallet in strength and resistance to bending because of the natural characteristics of plastic.
Also, since the pallet for a fork lift is, as described hereinabove, a hollow body having a fork-inserting mouth, a one-step molding process, such as, for example, an injection molding process using a thermoplastic material, would require a metallic mold equipped with a sliding core. One-step injection molding of a pallet is very difficult with conventional molding machines because they are so large.
Furthermore, it is difficult to obtain a plastic pallet which is characteristically comparable to the wooden or metallic pallets in bending strength, even using compression molding, extrusion molding and the like, because the pallet for a fork lift has the particular construction described above.
In addition, an enormous molding machine would be required to mold an item such as a pallet having large dimensions and weight. Therefore, such a pallet is remarkably expensive, both in its high initial cost and for its general maintenance.